V8 to a V4 Conversion: Get 40 Percent Better Gas Mileage
(Page 2 of 3)
July/August 1979
By MIchael Roach
The modification procedure was straightforward, and Joe easily undercut the standard 11 hours of flat-rate time allotted for a valve job ... a task which is very similar to the changeover. Then Joe and I went out for a spin. Though the V4 was a bit sluggish while accelerating to 20 mph, performance from that point and up to cruising speed was surprisingly good. (The mechanic loves to talk about the calculator-punching engineers who've computed that the four-cylinder powerplant shouldn't even be able to push the car's weight.) And I was amazed to find that the "new" V4 ran as smoothly as did the "full" V8 engine.
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But the real fruit of Joe's labor turns up as gas mileage. The reincarnated Plymouth garnered nearly 21 mpg — a big eight-mpg improvement, I was impressed enough to learn the steps necessary to transform a Mopar V8 (a Chrysler, Dodge, or Plymouth product with a 383-, 400- or 440 cubic-inch motor and two-barrel-carburetor) from Superman back into a mild-mannered reporter.
Getting Greasy
Start by stripping the motor as you would for a valve job. This task involves draining the coolant, loosening the exhaust system ... and removing the exhaust manifold, valve covers, rocker shaft assemblies (mark them "left" and "right" ), push rods, cylinder heads, intake manifold (including the carburetor), and valve lifters from cylinders two, three, five and eight. Clean all the parts and set the rocker shaft assemblies, the cylinder heads, and the intake manifold/carburetor unit on your workbench.
Then, find the left rocker assembly, and remove its rocker arms. Wrap the four oiling holes that serve the center two cylinders' rocker arms (cylinders three and five) with brass shim stock, and secure these makeshift seals with 1" hose clamps, as shown in Photo 1 (see the Image Gallery). Now replace the four outer rocker arms which serve cylinders one and seven. Then set the modified rocker assembly aside and locate the right shaft. Remove only the outer four rockers from the right assembly, and seal the oiling holes as you did those on the left side (see Photo 2). This procedure effectively disconnects the valves from the camshaft on cylinders two, three, five and eight.
Next — because you do not want compression to build up in the deactivated cylinders — remove the exhaust valves from the heads of the "dead" bores. In addition, to prevent air from being driven up through the valve guides and into the valve covers, block the guides with 3/8" x 3" National Fine bolts, washers, and nuts ... as shown in Photo 3. Torque the nuts to about 45 foot-pounds ... to ensure that they'll stay put and won't leak. And, again, leave those intake valves shut to keep any air from being pushed up toward the carburetor.
Unfortunately, you cannot just remove the valve lifters from the nonfunctional cylinders ... since the units ride in a pressurized oil gallery. And you can't leave the lifters in there, either, because the camshaft will knock them out. So, you'll have to fabricate "hydro-holders" for each of four sets of two lifters. A 4"-long piece of 1/8" x 1" x 1" angle aluminum — notched to fit the grooves in the lifters — will do the job. Drill and tap the block as shown in Photo 4, and bolt the "lifter locks" in position. This procedure will allow you to maintain oil pressure, while averting any undesirable moving part collisions.
